Arrays: Different image texture
You cant set a different texture for array's duplicates.

However, you can shift their UVs:



As you can see here, I have a texture of 1/3 ratio. Each third has a different pattern.
My array is set to make three different duplicates, and to shift their UVs of a third (1/3= 0,333...) on the V axis.

The result is quite usable.
All you have to do is a texture file containing your different textures aligned on one axis, adapt your UV to one area of the picture, and set your array's number of duplicates and U/V offset accordingly.